The present invention relates in general to a field effect transistor device operated as a field effect transistor oscillator. More particularly, the invention pertains to a two-terminal field effect transistor device. Even more particularly, the present invention relates to a two-terminal field effect transistor device that is adapted to readily replace a Gunn diode type device, or may be further adapted to replace other types of microwave oscillators such as Impatt, Baritt, Tunnel, Bipolar transistor, and 3-terminal FET oscillators.
Gunn diode devices and more particularly Gunn diode oscillators are now extensively used in many commercial applications. For example, such devices are used in microwave transmitters and local oscillators in communication systems and also in Dopler radar systems and in intrusion alarm systems. These devices may also find use in traffic control sensors and in industrial control systems.
For two-terminal devices, such as Gunn, Impatt, or Tunnel diode devices, the application of an appropriate DC voltage level is generally sufficient to produce negative resistance at the device terminals. This negative resistance condition exists up to microwave frequencies and all that has to be done is to provide a proper load for RF coupling.
With regard to the Gunn diode device, commercial microwave sources employ a packaged Gunn diode which may be mounted, for example, in a rectangular waveguide cavity. Up to the present, field effect transistors have not been used in the same package configuration basically because they are three terminal devices. The three terminal field effect transistor device, such as a GaAs FET, by itself will not produce any negative resistance by the application of a DC voltage and thus does not sustain oscillations. The field effect transistor requires a biasing network in order to operate as an oscillator and thus they are not capable of being packaged in the same manner as a Gunn diode and thus have not been used as a commercial microwave source in a package such as of MACOM type ODS-30.
It is also noted that although Gunn diode devices are relatively in-expensive, they have certain drawbacks associated therewith. For example, Gunn diode oscillators have relatively low efficiency and usually require a relatively high "turn-on" voltage.
Accordingly, it is an object of the present invention to provide a field effect transistor device constructed as a two-terminal device and operable as a field effect transistor oscillator.
Another object of the present invention is to provide a two-terminal FET device in accordance with the preceding object and which is adapted for packaging in substantially the same manner as the packaging for a Gunn diode device. In accordance with the invention, the field effect transistor oscillator of this invention is incorporated in a two-terminal package, an example of which is package type ODS-30.
A further object of the present invention is to provide a two-terminal FET oscillator device characterized by wideband mechanical and electronic tuning along with improved frequency stability with temperature.
Still another object of the present invention is to provide a two-terminal FET oscillator device that has a low operating bias voltage and operates with a higher efficiency.
Another object of the present invention is to provide a two-terminal FET oscillator device that is easy to handle, has acceptable noise level for most commercial applications, is very easily replaced, and can be manufactured at low cost.
Still another object of the present invention is to provide a two-terminal FET oscillator device that may be either in the form of an integrated circuit chip mounted in a standard package or may be embodied so that the oscillator circuit is integrated into a monolithic circuit, both of which are described in further detail hereinafter.